Beastly
by MistWing221
Summary: Sherlock makes a deal with the devil, and his little brother Sebastian is the one who ends up burned. However, the devil takes Sebastian in as his own and raises him to be his tiger. Demon!Moriarty - Mormor! (Disclaimer: I don't own any of the Sherlock characters)
1. Help, I'm Alive!

Sebastian stared up at Sherlock - his elder brother - with frightened blue eyes, gripping onto his stuffed tiger toy tighter as his attention was drawn back to the three boys setting up the devil's trap and alter in front of them. Sherlock only rolled his eyes at the reaction hardly believing that boy at his side was a Holmes let alone his younger brother - Sherlock had originally planned on coming here alone tonight, well, that was until his parents abruptly ended that idea, when they announced that they would be going out on a date night (Oh! How very quaint? He thought at first), but due to Mycroft being at school it was his responsibility to care for his younger brother.

When the older boy's had prepared the traps and lit the candles, they pulled their hooded cloaks on and began chanting, causing Sebastian's small heart to beat five times as fast. A whimper escaped his lips causing Sherlock to grab him by the wrist with an impossibly tight grip and turn him around, the elder brother bent down and glared deep into Sebastian's eyes. "Shut up or else..." He snarled, his silver eyes filled with hatred and deceit.

However the moment was cut short as the air began to grow cold and dark smoke started seeping through the wooden floor boards, causing it to creak. Sebastian was in tears by then, falling to the floor in fear and gripping onto his tiger as though it would protect him. The small boy watched as a dark figure formed in the centre of the devil's trap, everything about it screaming 'danger' however none of the boys, except Sebastian were frightened.

A boy with dark ravenous hair that could almost match Sherlock's stepped into the trap, his chest having been painted on with blood, the smoke demon seemed to react to this gesture in kind, possessing the boy quickly, before laughing like it was insane. Sebastian at that point had no doubt that it was, everyone in this room was, but not him. The boy slowly started to back away nervously, pushing his way towards the door before a hand reached out and grabbed his shoulder, causing him to scream only to realise that it was Sherlock's. "And where do you think you're going?" His elder brother cooed before pulling him back towards the beast.

"I would like to make a deal..." Sherlock stated immediately, causing the demon to jump with artificial joy, his eyes dark as it crept forward, towards the inner edge of the devil's trap.

"Continue..." The demon mused in a deep Irish accent.

"I want to know everything there is to know about the universe and everything in it, call it scientific curiosity, because I want to know it all..." He paused. "I also want my ability of deduction to improve..."

The demon hummed in thought before pacing the cage thoughtfully. "And what do I get in return? Hmm...Such great things come at such a high price..." The demon sung in a malicious sort of way, before turning back to face him.

"My brother..." Sherlock stated bluntly and without hesitation causing Sebastian to jump and look up at his brother with fearful eyes.

"Sherlock. No!" The little boy sobbed, gripping onto his tiger and shaking as Sherlock barely looked at him more interested in the demons response.

"What's wrong with him?" The demon enquired, eyeing the boy suspiciously, trying to identify any problems.

"Nothing. He is perfectly healthy. He is just - He is just a nuisance I would much rather be rid of..." Sherlock mused looking down at the crying child briefly. "So...Do we have a deal?"

The demon eyed the boy cautiously, before turning his attention back to Sherlock and nodding, more concerned about the little boy then the elder brothers deal. "Yes. Of course. Now. Give me the child!" He demanded before edging closer as the other boys backed away.

Sebastian looked up at Sherlock shaking his head repeatedly and trying to stick himself to the ground only to fail, when the elder Holmes simply picked him up and dangled him in front of his face in a taunting manner. "You will behave little brother..." He scowled, glaring at the boy and taking the boys tiger the moment he put him down within the devil's trap. Sebastian started screaming immediately, tears staining his face as he glared up at his brother and attempted to escape from the demons grasp.

"Is that all you want from me, Holmes?" He enquired, his voice almost as taunting and shrilling as a viper attacking its prey.

"Yes. We are done..." Sherlock stated darkly before steeping forward and breaking the line of the trap, allowing the demon to escape with its new vessel and his little brother.

The trip to hell was excruciatingly painful for the mortal boy, his body having been ripped apart particle by particle before being reassembled outside of a rather large mansion - armed with living gargoyles and terrifying statues that moved every time you blinked. It was a terrifying place for a child to be. The demon rushed to Sebastian's side, checking the crying child over for any scarring ascertained from the trip before finally pulling away. "Follow..." The demon ordered, not bothering to look back at the sobbing child; even after that brief display of compassion.

Sebastian's stumbled up the paved drive, trembling as the statues grew closer and closer to him until the demon dismissed them - the boy was lead into the mansion and up the ever spiralling stair case to his temporary room. "W-What are you going to do to me?" He whimpered having not strength to fight back without the support of his tiger.

"Nothing...well...That's not entirely true" The beast mused. "I will raise you. I will teach you how to survive in this world and when you are old enough you will become my bodyguard..." He paused. "But - Make no mistake, Sebastian - I /Own/ You" His voice rumbled growing dark as he looked down at the boy with an amused expression enjoying the child's fear. "Now! Sebastian. Tell me - Why do you like that 'tiger' of yours so much?"

The little boy flinched away immediately, looking up at the beast with a nervous expression before regaining enough of his composure to reply. "Because it protects me and Tigers are awesome, but I'm not allowed to have a real one though..." The little boy pouted. "Myc says that their dangerous and shouldn't be kept as pets but I tried to argue that I didn't want one as a pet. I wanted one as a friend because I don't have any friends. Sherlock always scares them off..." He sighed looking down sadly. "Myc brought me Tiger so I could have a friend but now he is gone..." His voice faded away and he looked down with sad eyes, knowing that he couldn't go back anymore. He was the demon's property. It owned him and as long as that was true - He could never go back.

"Well..." The beast sighed pulling out Sebastian's tiger toy from the satchel behind his back. "Tiger can't protect you, because he is a toy..." He teased before lowering the toy to the ground. "But a real tiger can..." He smiled softly once again (It was a smile that he only reserved for the boy), and waved his hand over the toy as it jumped to life causing Sebastian's eyes to widened in surprise. The boy immediately leaped forward and carefully tackled the cub to the ground playfully, hugging it tightly and pressing soft kisses to its furry head. "Thank you. Thank you. Thank you..." Sebastian praised gleefully.

Sebastian was to busy playing with his new tiger to realise the demons absence, however, it wasn't every long before it returned with a few blankets and a softer pillow. "Extra supplies considering we now have another guest staying with us..." The beast mused with a cunning glint in his eyes as it sat down beside the pair. "Have you decided on a name for your new friend yet?" He hummed reaching out to stroke the furry creatures head only for it to growl at him for getting to close to Sebastian. The boy giggled at the shocked expression left on the beasts face before pulling his tiger into his lap and humming for it to settle - Which it did almost immediately.

"You shouldn't do that..." Sebastian commented, stroking the cubs fur before looking up at the demon with a dark and menacing expression, that seemed to contrast with his otherwise angelic features.

It took away the demons breath at first, realising that he had underestimated the small child, before composing himself enough to respond in a challenging tone. "Shouldn't I?" He chimed, his blackening eyes becoming soulless as he stared down at Sebastian.

"Fine, but don't blame me if he attacks you because it would be your own fault.." The child refuted obviously used to arguing with his older brothers. "It would be because of your own stupidity anyway, demon..." He teased letting out a small hiss at the end, glaring up at the beast once again before his face changed back to being angelic and sweet.

"Aren't you just troublesome and misleading...Tiger..." He hummed tauntingly, seeming to like the nickname for the small child, it suited Sebastian - one for his personality, but also because of his behaviour.

"T-Tiger?" The child furrowed his brow and scrunched up his face annoyed, turning his attention back to the demon. "I'm not a tiger and that name has already been taken..." He grumbled, gripping onto the living tiger in his arms tighter.

"You can't just call a tiger, Tiger, Sebastian..." The demon argued, receiving a withering glare from the boy in response.

"Why not? I call you demon and you're a demon..." He hissed making a fair argument, that seemed to render the demon speechless once again.

"Fair enough, but I haven't given you an actual name to call me by..." It stated in reply only to realised that it would be wise to actually give the boy his name in case he got lost and didn't know how to get back to the mansion without him.

"James Moriarty..." Sebastian murmured against the tigers furry head. "That's your name, I read it on the sign outside. I can read you know..." He growled, almost sounding annoyed that the demon hadn't figured it out already. "I just prefer to call you demon because that's what you are..."

Jim looked hurt, and oddly enough his chest began to ache. "Very well..." He sighed, pulling the two closer despite their best attempts to struggle out of his grip; the tiger pawing at him with relatively sharp claws. "What must I do for you to like me? Hmm..."

"Let me go home!" Sebastian cried, causing the tiger to growl at Jim for hurting the boy in such away.

"You know I can't let you do that. A deal is a deal and your brother gave you to me to secure his..." He stated bluntly, before reaching down and cupping the boys face. "Why would you want to go back to them anyway? Hmm..."

"Because they're family and family means nobody gets left behind..." He whispered softly as tears started falling from his silver eyes, causing Jim's heart to break wanting to do nothing more then hold the boy against his chest and hug him until the pain went away. "Or forgotten...but they left me behind..."


	2. Casting Shadows

16 Years Later…. (Present day)

"Take the shot..." The booming voice rang through the earpiece, impatiently awaiting for the sniper to fire, however, being greatly disappointed for the second time. "Moran! Take the bloody shot..." The captain warned as he watched the target move from the sectioned area. Sebastian growled at the irritating sound buzzing in his ear, ripping out the clear earpiece and watching his target move through the scope. "Wait for it..." Sebastian whispered to himself, taking deep breaths as he waited for the perfect shot. He could feel Jim's shadow presence in the back of his mind, keeping him calm and telling him when to fire. "Wait for it, Sebastian..." Jim's phantom voice whispered in his ear causing the sniper to still - his trigger finger twitching with anticipation as he waited. "Calm yourself and wait for it, Tiger..." The demon's voice cooed again, before it wrapped its invisible hand securely around Sebastian's, the touch, exactly how the sniper remembered it. "Fire..." The voice hissed in his ear as Sebastian pulled the trigger, taking both targets out in a single shot.

He immediately pulled away from his perch, and looked around to find that there was nothing but air whistling in his ears. '_Don't be stupid, Sebastian' _- He thought. '_Why would he come back for you? You're nothing, but a pet to him.'_ His brothers voice taunted him in the back of his mind. '_You're nothing, but a demons pet, Sebastian. I doubt that you're even human anymore, Sebastian. SEBASTIAN. SEBASTIAN. SEBASTIAN_.' — "SEBASTIAN!" The voice screamed before the sniper was drawn back to reality by one of his comrades, John Watson, who was by his side whispering sweeting nothings in his ear, trying to calm down Sebastian's trembling form.

"It's okay, Sebastian - Everything is going to be okay…"

_Four years before..._

_"Sebastian dear it's your sixteenth birthday, we have to do something..." Jim exclaimed in an exaggerated tone, while drifting into the room with his usual demonic grace. _

_"I don't want to..." The unruly teen screamed marching past the demon with blazing fury as he dropped the full bag of popped birthday balloons on the floor. "You promised you wouldn't do anything, Jim. I don't want to celebrate it. That's final!" He growled, his fully grown tiger baring its teeth at the demon agreeing with its master. _

_"Not even if it meant going back to the surface? To London?" The demon mused, seeping closer to the boy and wrapping his arms around Sebastian's small waist. _

_"L-London? You mean it?" The teens mood seemed to improve drastically, his eyes widening in shock before turning around and kissing the demon repeatedly. "As in London, England right?" He enquired just wanting to make sure that it wasn't another trick. _

_"Yes, I mean London, England!" He grumbled, before kissing the teen back. "I guess I can't use the whole 'sweet sixteen and never been kissed' line on you though…hmm…?" James teased as he pulled away, with a jovial grin. "Get packed, ready and be down stairs before noon; also make sure your tiger is well fed and his things are packed away as well…I've arranged for him stay with Mistress Adler, whilst, we're away. I hope you don't mind…" He mumbled leaning down in front of the tiger and pouting. "You'll be a good boy now, won't you?" He meowed at the tiger only to get pawed in the face and tackled to the ground. _

_Sebastian bursted out into fits of laughter at the scene before him, over the years he had grown use to Jim's personality changes and attempts to bond, however, his tiger didn't share the same tolerance for the demon that he did. _

_"__How many times do I have to tell you not to tease the angry tiger…" Sebastian sighed, giving Jim the 'I told you so' look that he had mastered since the age of four. "I swear it's like dealing with a child!" _

_"__Fine. Fi - Hey! Wait! I am not at child…" He whined impatiently before shifting around uncomfortably, trying to push off the five-hundred pound tiger laying lazily on top of him. "Just get this furry beast off of me…" He screeched, only to get a deserving paw slap across the face._

_"__Awww….I think that means he likes you…" Sebastian teased before finally responding to the request. "Severus. Come!" He ordered as the tiger jumped off Jim's lap, springing forward towards its master. "Who's a good boy…" He cooed, leaning in and kissing the tigers cheek before the creature jumped up and gave Sebastian an awkward hug. "I love you too, Sev…"_

**Authors note: The chapter is small due to writer wanting to test the impact of flashbacks within the story - MistWing221**


	3. I'm coming home

(Present day)

"What the /hell/ happened back there?" John commented, looking up at the sniper with a worried expression. "You know I don't normally pry but…" The doctor bit his lip nervously, trying to approach his friend as best he could about the matter without spooking him further.

"But…" Sebastian mused, stepping closer to the man with a devious grin - there was something dark and possessing about the way he looked down at the doctor. It was almost demonic. It was almost cruel, which seemed foreign on Sebastian's angelic face.

John stilled completely, looking up at his best friend with frightened eyes - this was a side of Sebastian he rarely saw and his body was trembling in response. The sight was absolutely terrifying. "Bastian?" He choked out, shaking as he backed away slowly.

The sniper visibly flinched, glaring daggers at the doctor before letting out a vicious roar. "Don't ever call me that! You don't get to call me that. No one gets to call me that —" He repeated over and over again before pushing himself away as tears started to stained his face. _'Don't cry, Tiger. I don't like it when my tiger cries…_' Jim's ghostly voice played like mantra in the back of his mind until he felt a cold hand reach out and touch his shoulder.

"Sebastian…" John whispered softly, looking up at him with worried eyes; half filled with fear and half with compassion and worry for his friends sanity. "It's okay. It's okay, Sebastian. Just tell me what's wrong…"

The man whimpered slightly, looking back at the doctor with a frightened expression plaster across his face; his heart pounding in his chest as he let out a distorted sound. "Make them stop, John…" He begged. "The voices - His voice…"

"W-Who's voice?" He enquired in a calm tone, even though his hands were shaking with the fear that Sebastian might snap at any moment - He reached forward and wrapped his arms around the other man in a comforting manner. "You can tell me. You can tell me anything, Sebastian and know that no matter what I won't tell anyone. I promise."

"N-No. I can't —" Sebastian struggled, attempting to escape John's stone tight hold. "J-John. Stop…Let me go!" He cried, finally pushing the doctor away and composing himself enough to walk smoothly through the hot sand; wiping away the tears that lined his watery eyes.

John cursed under his breath before chasing after his friend with a growing concern - he had to tell someone but doing that could mean losing Sebastian all together. "J-Just tell me one thing…" The doctor murmured, catching up to the other. However this time keeping a steady distance. "Is there any relation between the voices and your nightmares?" He enquired before noticing the incredulous look the sniper was giving him, sighing as he reaffirmed the fact. "Yes, Sebastian I know about your nightmares - We sleep in the same tent after all.."

Sebastian stilled immediately, his body tensing at the memory before attempting to divert the conversation or at least end it quickly. "I thought that you weren't one for prying…" Sebastian muttered, keeping himself composed enough to look back at his friend - his heart dropping at the sight of those sad puppy dog eyes staring back at him, and the conflicted expression that the doctor wore on his war torn face. "Look - there just voices...voices projecting from memories of a time better left unspoken…" He whispered hoping that the other would just drop it.

John sighed, opening his mouth to respond before the sound of gunfire echoed through the small valley - both men stared at each other for a few brief seconds before bullets started whistling past them - Sebastian immediately moved to protect John, using his body as a shield when three bullets grazed his side before two tore through his chest and one (close range) penetrated his shoulder - nothing could describe the searing hot pain of fragmented metal tearing through bone, muscle and flesh. The sniper fell to the ground along with the doctor - his hands shaking, and arm weak as he reached for his gun, straining his mangled shoulder. "J-John…" He choked out, bitting back the bloodied scream that threatened to leave his lips.

"S-Sebastian…" John gasped from beneath him, his shoulder bleeding severely from a stray bullet. He felt the sniper grow heavy and limp on top of him; knowing exactly what that meant. "S-Sebastian…D-Don't you dare…Don't you dare die on me. Not here. Not like this…." He pleaded as he, himself began feeling light-headed from his own wounds. '_Please god let me live'_ John thought as his vision began to blur, unknowing to the fact the man above him was praying for the exact opposite.

Sebastian didn't fight - He welcomed death as though it were an old friend, his heart pounding in his chest as it strained itself in an attempt to keep the precious lifeblood flowing through his veins. He could feel John beneath him, begging him to stay awake - to keep breathing but he knew the other didn't understand. Sebastian wasn't scared. He had been waiting, wanting this for so long. Sebastian knew exactly where he was going. He was going home. He was going to Jim. He wouldn't be alone anymore. He would be free. "Home…" Sebastian whispered weakly as blood spilled from his lips. _'Don't worry, James…' _He thought as his blood drained away, staining the sand that surrounded his bloodied body. _'Your Tiger is coming home'_

**Authors note: This is another small chapter, they will start lengthening soon. No, Sebastian doesn't die in this chapter either - However the next chapter will explain why Sebastian is so welcoming to this kind of fate. It will also explain what ****happened between Jim and Sebastian. I hope you all enjoy reading this story as much as I enjoy writing it. Thank you to all those who have commented. I really appreciate the reviews. Thank you. -MistWing221**


	4. Miss me, brother?

**_Four years before…_**

"So…This is London?" Sebastian purred turning back to face the dark-haired boy, his expression jovial as he leaned in and kissed the demon's cheek softly. "Thank you…" He whispered quietly before pulling away; his eyes sparkling at the prospect of change.

James shied away from the kiss at first before turning back to the other with a weak smile etched into his porcelain skin. "This is London…" He sighed, reaffirming the fact - while contemplating on whether or not to tell the young teen that his family still inhabited the city. "Shall we?" He offered in a quiet tone, taking his tiger's hand and leading him through the cold streets until they arrived at their temporary flat. "221C Baker Street.." He hummed, tilting his head to the side nervously. "I know it isn't much…" '_But it's possibly the only place in London your family won't find us…'_ James finished the sentence in his mind.

"Oh! James…It's beautiful! It truly is…" Sebastian cooed as though he were in some ridiculous romance novel, moving forward and politely knocking on the door; his body seemingly less tense then before as he stepped back and leaned against his partner.

After a few silent moments the door slowly creaked open, revealing a well dressed woman in her mid-forties recently widowed - however still wearing her wedding ring, possibly to strike fear in bashful tenets. "Hello…" She hummed in a warm and inviting intonation of her faded cockney accent, it was welcoming to say the least - her eyes holding a spark of curiosity as she looked over the two seemingly young men at her door. "Can I help you?"

James stepped forward with a falsified grin; his dark brown eyes that could almost pass as black lightened slightly as he held out his hand in an inviting manner. "Ah…Mrs. Hudson I presume, it is a pleasure to make your acquaintance. My name is James Moriarty, I called you over the spare flat for rent…" He chimed in such a pleasant and alluring tone that it sparked an unusual and most unpleasant feeling in the pit of Sebastian's stomach. _Jealousy!_

The land lady seemed to notice the lost and uncomfortable expression on the other boys face, stepping aside and straightening back up as she gestured for the two to go in. "My. My. Where are my manners? Come in. Come in." She insisted jubilantly - patting Sebastian on the back as he walked through the threshold before closing the door behind them. She led them through the lower flat towards her small kitchenette; imploring for them to both take a seat while she made a fresh pot of warmed tea and biscuits.

Sebastian relaxed immediately as the dull ache of jealously left him being replaced with a new feeling of contentment and homeliness. It was perfect. This was perfect and most importantly, James was perfect. "Thank you, Mrs. Hudson…" He beamed happily, his dark atlantic blue eyes fixing on the warm tea that his new land lady was preparing. "Can I help with anything?"

"No. No. Its fine, dear…" She replied sweetly, collecting three mugs from the top cupboard and placing a few biscuits on a small plate. "So…What brings you two boy's to London?"

"Well…" The demon piped up. "It's Sebastian's sixteenth birthday in a few days, and he wouldn't accept any of my gifts - didn't really want to celebrate it at all actually…" He huffed turning back to face the glaring teen. "So…I offered to bring him here. Its been almost twelve years since he last saw London, you see…" Jim informed before being cut off by Sebastian - who elbowed him in the side, temporarily winding the demon.

"My family moved away…" Sebastian stated quickly; refusing to show the invisible ache of mentioning his family at all - even in such a minuscule way. The memories of that night still haunted him in his sleep; even though he was with Jim now, even though he was safe. The mere thought of his brothers unforgiving and cruel betrayal that night gave him chills.

He was thankful that Mrs. Hudson didn't pester them further on the subject - instead deciding to change the topic to something much more pleasant and less pressing towards Sebastian. "How long are you planning to stay? I'm sure I can extend your lease for as long as you wish…" She advised before setting down the tray of warm tea and jammy dodgers on the table.

Sebastian didn't hesitate as he leaned forward and collected the warm mug of tea before looking at the biscuits curiously. "I-I'm sorry to ask this…but what are they?" He blushed slightly, feeling embarrassed about his own comment.

Jim bit back an unadvised titter as he watched his tiger turn scarlet, embarrassed that he didn't understand what the biscuits were. "They're jammy dodgers, Bastian…" He hooted in response; a cunning grin edging itself across his pale face, and lighting up his devilish features. "Biscuits. You eat them…" He shook his head trying to shake off the odd feeling he was expressing towards his pet.

"Oh…" Sebastian replied red-faced as he bit into the biscuit. "That makes sense…" He confessed, taking a sip of his warm tea. "This is all very lovely, Mrs. Hudson…" He diverted the conversation again; looking around the small space with wondrous blue eyes. "Do you live here alone?"

"Thank you, dear…" Martha praised before looking down at the golden wedding band still wrapped around her finger. She let out a small thoughtful sigh before taking a sip of her tea and nodding. "Yes. I've been looking for new tenets for awhile ever since my husband passed…"

"Oh…" The teen gasped again feeling sympathetic for the land lady. "I'm so sorry, was it recent?" He added hoping that he didn't just open old wounds.

"Yes, but don't be sorry, dear. He wasn't very kind. Cynical really" She elaborated in a daunting tone before looking back up at Jim. "You've gone awfully quiet…" Martha mused, her demeanour changing significantly; from sadness to curiosity.

"No, I haven't…" The demon grumbled, looking between his tiger and the land lady before letting out a loud yawn. "I'm just tired, it was a very long trip…" He whined turning to face the other teen, and pouting childishly "If it's alright with everyone. I think I might retire to bed…" James announced before Martha handed him the key. "Thank you…" He acknowledged before turning to face, Sebastian. "Coming, Tiger?"

By six the next morning, Sebastian was dressed and ready for his run; looking back at the sleeping demon sprawled across the bed with a cheshire cat grin before pulling on his grey track hoodie and walking outside. The air was crisp against his pale face causing cold shivers to run down his spine; his body still trying to adjust to below average temperature. "London…" The teen whispered again in wonder, looking around and taking the sights in before closing his eyes; everything was still how he remembered it from his neglected childhood memories.

The boy soon went to turn only to bump into another, falling to the ground dumbfounded for a few moments before looking up and seeing a ghost._ 'His intelligent eyes still the same majestic silver as they were that night, his hair still styled as an unruly mop of dark curls, and lips still as red as blood.'_ His brother. Sherlock Holmes stood before him, glaring down at the teen with a calculating expression before it changed to one of complete shock. "S-Sebastian…"

**Authors Note: I hope you all enjoyed the chapter - the next will be taking place in the present - MistWing221**


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